Method and apparatus testing IC chips for damage during fabrication

Abstract

An approach using two terminal current measurements, preferably in a cyclic current-voltage sweeping procedure, and specialized test structure, is shown to be very useful in detecting processing induced changes in poly-Si/ultra-thin SiO 2 /substrate Si structures. The charging current structure discernible in this approach is seen to have different features depending on processing history of the device. This is shown for the specific case of plasma gate definition etching with or without annealing.

What is claimed is: 
     
       1. A method for measuring properties of a microelectronic device, comprising the steps of: (a) applying a voltage to said device;   (b) changing said voltage in predetermined increments, with predetermined time intervals between incremental changes in said voltage, until a first limit voltage is reached;   (c) measuring during said time intervals current induced within said device as a function of voltage;   (d) determining said properties from one or more charging current peak structures occurring in said current measurements; and   (e) determining density of defects within said device from a magnitude of said one or more charging current peak structures.   
     
     
       2. The method of step 1 including the additional steps of: (a) once said first limit voltage level is reached, holding said first limiting voltage for a prescribed period of time;   (b) reversing the sense of said voltage incrementations;   (c) incrementally changing said voltage in said reversed sense, with said predetermined time intervals between said incremental changes, until a second limit voltage is reached; and   (d) measuring during said time intervals current induced within said device.   
     
     
       3. The method of claim 2 wherein said voltage is first incremented in a positive sense. 
     
     
       4. The method of claim 3 wherein the magnitudes of said incremental changes of voltage are equal. 
     
     
       5. The method of claim 3 wherein said predetermined time intervals are equal. 
     
     
       6. The method of claim 3 wherein said first and said second limit voltage levels are related to microelectronic device operating voltage limits and are equal in magnitude and opposite in algebraic sign. 
     
     
       7. The method of claim 1 further comprising the step of determining additional charge within the device from the position of said charging current peak structures with respect to said applied voltage. 
     
     
       8. The method of claim 1 wherein changes in said charging current peak structure are used to monitor processing and processing equipment. 
     
     
       9. The method of claim 1 wherein said voltage incrementation time intervals are equal and said predetermined time intervals are equal. 
     
     
       10. A method for measuring properties of a microelectronic device, comprising the steps of: (a) applying a voltage to said device;   (b) changing said voltage in predetermined increments, with predetermined time intervals between incremental changes in said voltage, until a first limit voltage is reached;   (c) measuring during said time intervals current induced within said device as a function of voltage;   (d) determining said properties from one or more charging current peak structures occurring in said current measurements; and   (e) using changes in said charging current peak structures to monitor processing and processing equipment.   
     
     
       11. The method of step 10 including the additional steps of: (a) once said first limit voltage level is reached, holding said first limiting voltage for a prescribed period of time;   (b) reversing the sense of said voltage incrementations;   (c) incrementally changing said voltage in said reversed sense, with said predetermined time intervals between said incremental changes, until a second limit voltage is reached; and   (d) measuring during said time intervals current induced within said device.   
     
     
       12. The method of claim 11 wherein said voltage is first incremented in a positive sense. 
     
     
       13. The method of claim 12 wherein the magnitudes of said incremental changes of voltage are equal. 
     
     
       14. The method of claim 12 wherein said predetermined time intervals are equal. 
     
     
       15. The method of claim 12 wherein said first and said second limit voltage levels are related to microelectronic device operating voltage limits and are equal in magnitude and opposite in algebraic sign. 
     
     
       16. The method of claim 12 further comprising the step of determining additional charge within the device from the position of said charging current features with respect to said applied voltage. 
     
     
       17. The method of claim 10 wherein said voltage incrementation time intervals are equal and said predetermined time intervals are equal. 
     
     
       18. A method for measuring properties of a microelectronic device, comprising the steps of: (a) applying a voltage to said device;   (b) changing said voltage, with predetermined time intervals between changes in said voltage, until a first limit voltage is reached;   (c) measuring during said time intervals current induced within said device as a function of voltage;   (d) determining said properties from one or more charging current peak structures occurring in said current measurements;   (e) determining density of defects within said device from a magnitude of said one or more charging current peak structures; and   (f) using changes in said charging current peak structures to monitor processing and processing equipment.   
     
     
       19. The method of claim 18 including the additional steps of: (a) once said first limit voltage level is reached, holding said first limiting voltage for a prescribed period of time;   (b) reversing the sense of said applied voltage;   (c) changing said voltage in said reversed sense, with said predetermined time intervals between said changes, until a second limit voltage is reached; and   (d) measuring during said time intervals current induced within said device.   
     
     
       20. The method of claim 19 wherein the magnitudes of said changes of voltage are equal.